What do dealers mean by "dark bore"? Is it a good thing or a bad thing? I know what the bore is (the barrel). A good bore is shiny/reflective, right? When I bought my Norinco they put a bore light in it and the salesman said "Oh yeah, like a mirror". Clarification?

When powder charges start to erode the metal surface, inside the bore, it hapens most intensly nearest the chamber where the heat from the burning propellant's the hottest - but it occurs throughout the bore.

A "dark bore" means the barrel has started to erode from the wear of the powder granules (which are a little like sand, and the friction of the projectiles, but not enough yet to actually rust or to pit underneath some rust.

The "pitting" is the pinholes left after the rust has been removed from the barrel - or any other surface, for that matter.

The darkness in a "dark bore" comes from the rough bore's failure to reflect as much light as a "bright, shiney bore".

You may also come across the term "ringed bore" - more common with rimfires - that looks like a circle around the other end of the bore opening when the bore is looked through, that can be almost anywhere in the bore (front-to-back) - usually caused by shooting through a bore obstruction, like a previous squib load, where the bullet never made it out of the muzzle.

Might mean what the seller wants it to mean. If he grades a whole lot of guns into that category, maybe they vary from just turned dark from surface rust up to badly pitted and not very good shooters. Since alot of sellers like to be optimistic sounding on their descriptions, I would suspect the lowest grade of "dark bore" until you see it yourself. You can shine up a bore somewhat that is a bit on the dark side, but you cannot fix pits. Pits are a problem more so with lead bullets as compared to jacketed. A frosty looking bore could shoot jacketed bullets acceptably, but leading would be accelerated on a rough surface created by tiny microscopic pitting or roughness that takes the shine away. Even shiny bores might have throat erosion issues. Looks fine looking down the muzzle, look in the other end, too. Don't know what your Norinco is. But if it is an SKS it would have a chromed bore and those stay shiny for a long time and resist pitting etc. I have a WW2 Japanese rifle that has a perfect chromed bore that is quite shiny. Good shooter. I have a Beretta 9MM that was fired alot and the chrome plating shows some wear and dullness from that.

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You answered your own question. A dark bore is one that is not shiny. The darkness is caused by the fact that dirt and/or rust does not reflect light. In most cases, saying that a rifle has a dark bore means that an effort has already been made to clean out normal dirt and fouling, and that there is either live rust or old rust that has resulted in pitting or the eating away of the barrel steel in tiny spots.

Most of the dark bores seen in military rifles are not the result of wear or erosion but the result of firing with ammunition having primers made with a corrosive compound. When those primers are fired, the salt is released into the barrel and if moisture is present, the result will rust the barrel, just like common table salt will rust steel. (In spite of some confusion, corrosion and erosion are not the same thing. The former is essentially rust; the latter is eating of the steel by heat.)

If the barrel is pitted, whether lightly (frosted) or deeply, or eroded, there is no practical way it can be restored other then drilling it out for a larger caliber and re-rifling it. There is no magic ointment or secret sauce that will restore that barrel. Once steel is gone, it is gone.

I once owned a Lee-Enfield that was quite pitted for the first third of the barrel beyond the chamber, yet it shot very well (though I was never a particularly good shot). Apparently the part of the barrel that makes the most difference is the part near the muzzle and you will see frequent references to the importance of protecting that part of the barrel, or rather the bore of that part of the barrel.

When I was in the army they stressed in basic training that you needed to clean the barrel for two or three days in a row or something like that just to get out all the metal fouling, which is not the same as corrosion, though I've never understood why that was considered so important.

I think they meant if you got metal fouling in the barrel (like shavings of jacket, bits or filings off the cases or whatever, if you dont get most of these out, you might fire a round which cant push this stuff out of the muzzle in front of the projectile, so the projectile will "overtake" the crud and probably bulge the barrel in the process. It might be so small a bulge that your eye cant see it, wherever it is along the length of the barrel, you will lose overall muzzle velocity, and if it is in the last quater of the barrel (muzzle end) your accuracy will suffer.

From what I have heard, water is as bad if not worse. if you have water in your barrel and shoot, the projectile can try to "overtake" the water, which has no where to go and cant compress, so you can end up with a nice bulge in your barrel too

Muzza

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Muzza
If you cant blind them with brilliance, Baffle them with BS
Be alert...... there is a shortage of LERTs

If you are looking to buy a C&R gun, you will probably run into the 'dark bore' description. These guns can have a lot of dirt built up in the barrel. When you get it, you 'clean' the barrel before shooting.

You will see a lot of dirt come out and eventually, you will get patches that look clean.

Then you shoot a bit and as you clean, you wonder where the black came from on the patches as you did not shoot a ton of bullets in there.

Old miltary guns, with that build-up, will still have built-up crud under what you took off. Firing the gun will heat the barrel and loosen some more of the crud.

One of the things that you can do to help the process is to get one of those foaming cleaners and foaming copper removers and use that. Then, after you take that out, run a solvent soaked patch through the barrel and let it sit for a while, then attack it with brush and patches, and do it over again. Eventually, you will get the gun to the point where it is almost clean as new, and then, you can see what kind of pitting you have, or not. Just depends on the luck of the draw.

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